A typical longwall mining apparatus such as described in German patent documents 3,318,360 of P. Heintzmann, 3,514,439 of G. Blumenthal, 3,743,239 of G. Blumenthal (U.S. equivalent Pat. No. 4,883,322), and 4,004,488 of K. Plaga (U.S. equivalent Pat. No. 5,688,796) has a main conveyor chain that extends as parallel front and rear stretches along a face being worked between a pair of turnarounds. One of the turnarounds is in a takeoff shaft or heading leading back from the face and containing a takeoff conveyor and the other is in an access shaft or heading that normally extends parallel to the takeoff shaft. The rear stretch of the chain runs in a conveyor trough parallel to the face and the front stretch runs along the face being worked. Conveyor/cutting elements mounted on the chain are set in the front stretch in a vertical position in which they engage the face and plow material off it so that this material drops into the conveyor trough. In the rear stretch the conveyor/cutting elements are moved to a horizontal position in the trough where they push the recovered material along to the end of the trough where a takeoff conveyor extending away from the face in the takeoff shaft carries away the recovered material.
At each turnaround there is a wheel or sprocket over which the chain is engaged. As a rule a main drive is provided in the main takeoff shaft where there is substantial room, and an auxiliary drive is provided at the other turnaround in the small access shaft at the other end of the face being worked. A separate device at the takeoff-shaft turnaround transfers the material from the conveyor trough to the takeoff conveyor.
In the standard prior-art system such as described in above-mentioned German patent document 3,318,360 the turnarounds each have a ramp so that as the elements move in the access-shaft turnaround from the front stretch to the back stretch they move from the erect to the recumbent position and at the takeoff-shaft turnaround they move from the erect to the recumbent position. These systems are, however, fairly bulky and expensive, in particular as regards the required angled wheels at the turn-arounds.